In a curious twist on the usual story on how insects spread human diseases, us humans are propagating a virus that deforms the wings of bees. And like most modern disease stories, this one is international, thanks to the commercial transport of honeybee colonies around the world.
Bees are needed to pollinate plants, but bees are also on dying all over the world. The answer, of course, is to make a buck by shipping bee colonies from place to place, where they will go about their busy-business of pollination, before being shipped off to the next venue. It’s like a national or international tour, only with bees instead of rock stars, and the mite Varroa destructor in place of groupies.
Deformed wing virus and the Varroa mites that carry it "are a major threat to the world’s honeybees," says a new study out of the University of Exeter, published in Science. The European honeybees that tour the world are originally from East Asia and have made their way through Europe to the Americas and Hawaii, and then on to Australia and New Zealand, originally brought along by European settlers.
The disease, which—as its name suggests—deforms the wings of the bees, is fairly resistant to direct transmission between bees, and on its own would be little more than a nuisance. The Varroa mite which carries it, though, is a much more dangerous. It infects a high number of bees, causing whole colonies to collapse when they are overwintering, and also eats bee larvae.
The mites emerged as a problem in the late 20th century and are responsible for the current pandemic thanks to the increased movements of colonies. And the problem isn’t just contained within these roving colonies. Like hippies following a never-ending Grateful Dead tour, some of these parasitical mites drop out along the way and insinuate themselves into local colonies.
To slow and hopefully halt this global free-ride, the study recommends
"tighter controls, such as mandatory health screenings and regulated movement of honeybees across borders." The authors also call for Varroa-free refuges "for the conservation of wild and managed pollinators," in an effort to maintain non-infected populations.
The problem seems set to continue, though. As long as there are too few bees to pollinate crops naturally, they will keep being shipped around the world. And for as long as that happens, local colonies remain under threat, and unable to restore themselves—a classic Catch-22-style bind.